Movie fans know not to leave the theater until the very end during a Marvel film. It was Nick Fury's appearance in the first "Iron Man" that started the long march to "The Avengers" in the first place.

So it should come as no surprise that there's something waiting for ya at the end of Earth's Mightiest Heroes' new flick. (You'll want a minute to hang out in your seat collecting your breath anyway.)

But in case you stayed and wondered, "who is that dude hanging out on the meteor at the end?" luckily you've come to the right place.

SPOILER ALERT: Stop reading now if you don't want the answer!

That was THANOS and setting him up as a future bad guy is fan-frickin'-tastic. Here's why:

Who Is Thanos?

Thanos is a big-ass alien beast (an Eternal from Saturn's moon of Titan, if you must know) who is obsessed with death. (Hence the name, you Hellenistic scholars.) He's obsessed with death as a concept, but also obsessed with Death, the personification of mortality who, in 1970s Marvel funnybooks, was a boobalicious grim reaper type.

In order to impress her favor, Thanos loves to cause mass destruction and – if he gets his hands on the powerful device known as the Infinity Gauntlet, well, let's just say it's gonna be a bad scene.

The Infinity Gauntlet was actually seen by folks with sharp eyes and pause buttons up in Asgard in the movie "Thor."

Why Thanos Appearing in 'Avengers' Is Awesome

Even though Christopher Nolan's "Dark Knight" films are masterpieces, Marvel, basically, beat DC. Nolan's films are not part of a larger universe. But the Avengers actually assembled, even though it seemed like a pipe dream just five years ago. Having Thanos show up at the end of "The Avengers" is kinda like a middle finger to DC.

Thanos, ya see, is a bit of a ripoff of DC's Darkseid, who, if there ever were to be a Justice League movie, would be the natural villain. Considering how much the two look alike, that's somewhat impossible now. If Thanos becomes a major player in Marvel movies, people would catch a glimpse of Darkseid in TV commercials and think, hey, isn't he the guy from the other movies? Advantage: Marvel.

Who Should Fight Thanos?

The post-"Avengers" Marvel Movieverse stands at an interesting crossroads. And if producer Kevin Feige were about to land in my backyard and hand me the green ring of power to control everything, if I may mix my Universe metaphors, here's what I would do.

I would keep Captain America, Iron Man, The Hulk, Hawkeye and Black Widow down on Earth. Let them have somewhat more conventional adventures. . .maybe with the return of Red Skull. (I would also get that Hawkeye/Black Widow movie announced stat.)

The rumored Doctor Strange and Guardians of the Galaxy films seem like an appropriate place for all this weird interstellar nerdery. Basically, let the "bigger" films with the known characters have the larger budgets and the expectation to bring in huge crowds. Let the true, dyed-in-the-wool mouth-breathing comics dweebs (like me!) have the lesser known characters' films to get all sci-frenzied with this Infinity Gauntlet crap.

Lastly, Thor ping between the two when need be. "Thor 2," already in production, is hopefully going to be the gateway drug to the crazy outer space stuff that some of us asthmatics are really excited about. But he can still show up for a big fight on Earth in "Avengers 2" when the time comes. Thunder Gods, in case you didn't notice, tend to come and go where they please.

Come back every Thursday for more intergalactic musings on Planet Fanboy and follow its fearless leader Jordan Hoffman on Twitter!